Final answer:
Matteo is exhibiting the defense mechanism of repression according to Sigmund Freud's psychoanalytic theory.
Step-by-step explanation:
According to Sigmund Freud's psychoanalytic theory, the defense mechanism that Matteo is exhibiting in this scenario is repression. Repression is the defense mechanism in which anxiety-causing memories are blocked from consciousness.
In Matteo's case, he was bitten by a dog when he was 2 years old, which caused a traumatic experience. As he grew up, he developed an intense fear of dogs. However, he does not remember the incident because his mind repressed the memory to protect him from the anxiety associated with it.
Repression is a common defense mechanism that helps the individual to cope with overwhelming or traumatic experiences. By repressing the memory of the dog bite, Matteo's mind shields him from the anxiety, but it also leads to the development of an intense fear of dogs.